An ever increasing number of prospective home buyers today are choosing factory built manufactured homes over conventional stick-built homes. Today's prefabricated manufactured homes, with their improved construction methods and quality control, can now closely approximate the look and feel of a conventional stick-built home, and can be constructed at a substantial savings compared to a conventional home.
Originally, most prefabricated homes were very similar to the common single width trailer homes, and consequently the living space was long and narrow with rather meager floor space. However, in order to accommodate the wishes of customers who preferred the larger and wider floor space of a traditional home, many of today's manufactured homes are built in modules or sections that are shipped to the home site and joined together on an existing foundation to form a double wide home.
Typically, each half of the home comes equipped complete with exterior and interior walls and flooring, a roof, and many fixtures including the plumbing and appliances. An axle and wheel assembly is attached to each half so that the unit can be separately towed to the home site and joined together over an existing foundation. Accordingly, the floor frame assembly must be strong enough to support the assembled home over a typical foundation, and must also be strong enough to survive the rigors of being shipped from the factory to the home site without excessive flexing, which could damage the superstructure, the interior walls, and the fixtures. Furthermore, the floor frame must be designed so that the two halves can easily be joined together at the home site with a minimum of additional on-site labor.
Floor frame assemblies for shipping manufactured homes are generally well known in the art, although their designs differ greatly. One prior art design is the perimeter frame design, which consists of a rectangular box like frame built from two main longitudinal members that form the outer edges of the frame. The main members are connected by a series of cross members, typically wooden trusses, that span the entire width of the frame. These wooden trusses are very labor intensive and require an extensive amount of bracing and gusset plates in order to make the frame stiff enough to tow, and hence the perimeter frame design is very expensive to produce. Also, the perimeter frame design requires an extensive amount of on site assembly, which increases labor costs and undermines quality control because on site labor is difficult to monitor. One variation of the perimeter frame design consists of simply using floor joists instead of trusses. The floor joists are mounted or "stacked" on top of the main members, and therefore this design requires more vertical space, which means less headroom in the basement, less headroom on the living quarters, or a higher unit that is more expensive and more difficult to transport.
Another prior art design uses two elongated support beams spaced inwardly from the outer edges and are connected by a series of cross members. The cross members are typically made of metal in order to simplify installation and minimize weight, and extend outwardly from the elongated support beams to the edges of the modular unit. However, the design of the outer edge of the outrigger complicates the attachment of a sill plate, and also makes it difficult to attach the ends to an adjacent unit to form a double wide home. Accordingly, this design is more suitable for single width homes. Finally, if the ends of the outriggers are placed directly over the foundation wall, the bottom of the elongated supports hang down into the basement and interrupt the ceiling height in the basement. Accordingly, either the basement needs to be deeper or the builder must add a course of bricks to two sides of the foundation in order to obtain the desired amount of headroom in the basement.
Accordingly, manufacturers of manufactured homes require a floor frame assembly that is easy to manufacture, strong enough to ship to the job site, and strong enough to span fairly large foundations with minimal extra support. Manufacturers of manufactured homes also require an improved floor frame assembly that minimizes the amount of on site labor required, and that can quickly and easily be joined with a like floor frame unit to form a double wide manufactured home.